Rat heads are one thing but don't expect a human head transplant any time soon

Xiao-Ping Ren and Sergio Canavero, the surgeons planning the first human head transplant

Sergio Canavero/OOOM

Earlier this week, an Italian scientist made headlines because of his involvement in a shocking new study. He and a team of Chinese researchers claimed to have successfully transplanted the head of a rat onto another rat’s body.

The paper in question, published in the journal CNS Neuroscience & Therapeutics, was praised as being a step towards human head transplant surgery. But neuroscientists around the world are wary of these claims.

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The method demonstrated in the new paper makes progress in one particular technique called ‘cephalosomatic anastomosis’, or CSA. CSA involves anaesthetising an animal, cutting its spinal cord and keeping the brain alive until it can be attached to a donor’s body. This has been done before.

Sergio Canavero and his team repeated this procedure, attaching a small rat’s head to a larger rat’s body several times. The head was kept alive for a few hours each time. According to experts, the main triumph in the paper was the ability to keep the organ alive until it was attached, using the blood supply from a third rat.

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“Keeping organs alive and intact during the transplant procedure is a very important part of transplants,” Dean Burnett, a neuroscientist at Cardiff University, told WIRED. “Any approach or data that can help improve this process would be of value.”

But this is where its value ends.

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“The current experiment seems to be purely to show that severed heads 'can' be kept alive and attached to another body, but that doesn't tell us much beyond the fact that it's physically possible to do this,” Burnett said.

“It's a pointless exercise in microsurgical technique,”Paul Zachary Myers, professor of biology at the University of Minnesota Morris, told WIRED.

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Canavero and his team attached a small rat’s head to a larger rat’s body

CNS

The problem is, while it is an impressive show of intricacy to be able to sew a rat’s head onto another rat’s body, the technique does not solve the main issue when it comes to head transplants: nerve regeneration.

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Our central nervous system's ability to regenerate neurons is key to our survival. People with spinal cord injuries, for example, can lose the ability to regenerate neurons and this can lead to early death.

“The problem is that the nerve is not going to regenerate well enough for long term survivability,” Dr Gordon Lee, plastic surgeon and director of microsurgery at Stanford Health Care, told WIRED.

How the rat transplant was done

The researchers took one very small rat, the head donor, and one very large rat, six times larger than the donor.

They anaesthetised them both. A third rat was used to maintain a blood supply to the donor’s head. Next, the team opened up the recipient rat’s neck and exposed the jugular vein and carotid artery.

As these were tied off, basically killing the recipient rat’s brain, the researchers inserted silicone tubes to travel through a pump to help maintain a steady blood pressure.

The rat was passed through a water bath to cool the blood to 31.5°C and to help the cells last longer without oxygen.

The scientists then connected the veins to the axillary artery and vein of the donor rat. When oxygenated blood started flowing from the host rat to the donor’s head, they opened up the donor’s chest, tied off the donor heart and lungs and basically threw away the body.

To finish the procedure, the team stitched the donor rat’s head to the back of the neck of the host rat. The rat died after six hours.

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Attaching a head onto a new body opens up a lot more problems compared to spinal cord injuries, which often concern only one or two connections.

“In the spinal cord there are millions of highly complex connections,” Burnett said. “Reattaching severed spinal cords is currently beyond us; attaching two that have never been connected before should be significantly more difficult. There's nothing in this questionable research that challenges this situation.”

Sergio Canavero has been dubbed ‘Dr Frankenstein’ because of his wild claims he will be able to complete a human head transplant by the end of this year.

Canavero had first said his patient would be Valery Spridonov, a Russian with the degenerative muscular condition Werdnig-Hoffman’s disease. Now, it seems, the candidate will likely be a Chinese citizen as that is where Canavero expects the operation to take place. The scientific community is deeply concerned.

“The concern many of us in the field have about this sort of work is that those involved appear to be charging ahead without a viable, demonstrated solution for the significant and unresolved technical challenges,” Dr Wael Asaad, assistant professor of neurosurgery at Brown Alpert Medical School, told WIRED. “And without sufficient attention to the ethical and social factors.”

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Whether or not the procedure to attach a human head onto another human body would pass any ethics board, is another question entirely.

“The argument here is to preserve a healthy mind/brain when a body is irreparably damaged, but this would mean having a healthy donor body on hand, which is quite a big ask in itself,” Burnett said.

But for now, with the techniques presented, it seems there would be no benefit to a patient. Even if the procedure can be done, the new head would not be able to be kept alive for long.

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“Without a radical breakthrough in neurobiology, [head transplants are] not possible,” said Myers. “Such a breakthrough will not come from playing games with vascular surgery, no matter how intricate.”

Canavero has explained his surgical technique in a TED Talk, in what could be seen as an attempt to gain further notoriety. He hopes to keep the patient in a coma for a month after surgery, then he thinks they will wake up and be completely functional. Dr Lee said this was the stuff of “science fiction”, and others agreed.

“When someone makes an extreme claim,” Burnett told WIRED, “my rule of thumb is this: if they haven’t provided robust scientific evidence, but they have done a TED talk, alarm bells should be ringing.”